The present invention relates to polyamide textile finishing and more particularly to the improvement in the flame-resist and smoke emission properties of natural polyamide fibers.
Naturally occurring polyamide fibers, for example the wool of sheep, display a high degree of natural flame retardancy because of their relatively high nitrogen and moisture content, high ignition temperature (570.degree.-600.degree. C.), low heat of combustion, low flame temperature and high limiting oxygen index.
The performance of wool fabrics in the various test methods currently in use depends on the specified test method and fabric construction. A horizontal test method is much less severe than a 45.degree. or a vertical test. Most wool fabrics will pass a horizontal test but may not pass some 45.degree. or vertical tests. The influence of fabric construction is also very important, the denser and heavier the fabric the lower the flammability. For example, a conventional tufted pile wool carpet will pass the American "Tablet Test" (DOC FF- 1-70, DOC FF 2-70), while a carpet in the same material but having a loose or a longer pile may fail the same test.
It follows that wool in some cases needs a flame-resist treatment in order to pass a particular flammability specification and test method. Curtain and wall coverings in public buildings, aircraft furnishings and blankets, furnishings and curtains in general transport, protective clothing and carpets of shag pile construction and low density are products which may require treatment.
It has previously been proposed to apply titanium compounds to textile fibers as flame-proofing agents. Such compounds are not always suitable when wool fibers are used because they can cause yellowing. Moreover, although the process is satisfactory for many purposes, it is not entirely suitable for the manufacture of bleached wool articles.
In addition, the smoke emission characteristics of textile furnishings have recently come under careful scrunity by environmental agencies. Recently, the Federal Aviation Administration published proposed smoke emission standards for aircraft textile furnishings. Previously, these furnishings were only required to meet a vertical flame test standard.